Regular blood transfusions is a lifetime treatment for blood disorder such as thalassemia and it can lead to the iron accumulation within the organs. Iron accumulation in the brain can cause toxicity by increasing reactive oxygen species (ROS) and altering apoptotic signal. However, the impact of the iron overload in cognitive function is still unclear. The purpose of this study is to investigate the effects of iron overload to the cognitive function of mice. Three groups of mice were divided into three groups with different dosing of iron injections (0, 0.1, and 0.3 mg/mice). Iron was injected intraperitoneally for 19 days. A special experimental maze was used to assess the cognitive function. The test was repeated three times; before injection, the 6th day of injection, and the 11th day of injection. After 19 days of injections, brain weight was measured and brain histology examined. Our results showed that cognitive function was impaired after iron injections. Cognitive function test indicated that the time required by group 1 during the first test were 265.20 ± 47.11 seconds, during the second test were 123.20 ± 18.33 seconds, and during the third test were 151 ± 45.80 seconds. Next, the time required by group 2 during the first test were 254.60 ± 44.16 seconds, during the second test were 176,60 ± 32.54 seconds, and during the third test were 259.60 ± 63.28 seconds. Then, the time required by group 3 during the first test were 260.20 ± 44.90 seconds, during the second test were 241.20 ± 32.65 seconds, and 272.40 ± 65.79 seconds during the third test. The data analysis indicated insignificant changes between group 1, group 2, and group 3 with p-value 0.068. There were no significant changes in brain weight and brain histology among all groups. We conclude that iron overload can cause alteration of mice cognitive function without change in brain histology.